Support authors with non-utf8-encoded names

Ref. task cc5bffe6-926f-43d1-be18-a4f1e02002b3 (miyamuko/pacman)

Needs a schema change to make authors bytea instead of text.

---

Migrated from T65 (view on Phabricator)

added Git loader Storage manager priority:High labels

changed the description

mentioned in commit swh/devel/swh-storage@e80adb87

mentioned in commit swh/devel/swh-objstorage@da274930

closed

mentioned in commit swh/devel/swh-loader-git@0ddd630f